Portable computing devices (e.g., laptops and smart phones) are commonly being used to broadcast content to auxiliary displays (e.g., projectors and televisions). A common use-case scenario involves a user loading a slideshow presentation onto his or her portable computing device, connecting the portable computing device to an auxiliary display, and then causing the portable computing device to output the slideshow presentation to the auxiliary display. Various interfaces can be used to connect portable computing devices to auxiliary displays, including Digital Visual Interface (DVI) cables and High-Definition Multimedia Interface (HDMI) cables. More recently, however, network-based interfaces are being implemented and enable users to share their content on nearby auxiliary displays through local networks (e.g., a WiFi network). One example of a network-based interface includes Apple's® AirPlay®, which enables AirPlay®-equipped portable computing devices (e.g., iOS-based devices such as iPhones® and iPads®) to broadcast content to AirPlay®-equipped components (e.g., Apple TVs®).
Although the foregoing approaches provide a convenient mechanism for individuals to share their content with others, privacy concerns unfortunately continue to be a problem. For example, when a user “mirrors” his or her iPhone® to an auxiliary display, the entire user interface displayed on the iPhone® is replicated at the auxiliary display and can be seen by others. Oftentimes, when being mirrored, the iPhone® continues to receive and display personal data (e.g., text messages), which can be problematic for the user (e.g., when sharing a slideshow presentation with his or her colleagues at work). One approach commonly taken by users to reduce privacy exposure involves manually closing applications and disabling notifications prior to broadcasting content to auxiliary displays, but this is a cumbersome and inefficient process. Moreover, the typically large number of applications that execute on portable computing devices makes it difficult for users to cover all potential avenues of privacy exposure.